An Intensely Itchy Unilateral Rash on a Man’s Lower Leg: What’s the Cause?

AUTHORS:
Alexander K. C. Leung, MD, and Benjamin Barankin, MD

CITATION:
Leung AKC, Barankin B. An intensely itchy unilateral rash on a man’s lower leg: What’s the cause? Consultant. 2016;56(11):1013-1014.

A 28-year-old man presented with a 6-month history of an intensely pruritic area on the right lower leg. He had a history of eczema and asthma.

On examination, there was a large, erythematous, poorly defined, lichenified plaque with overlying scales and mild excoriations on the right lower leg.

What's your diagnosis?

1. Tinea corporis
2. Nummular eczema
3. Lichen simplex chronicus
4. Psoriasis

Answer and discussion on next page.

Answer: Lichen Simplex Chronicus

Lichen simplex chronicus (LSC), also known as localized circumscribed neurodermatitis, is a chronic, inflammatory, pruritic, localized skin disorder characterized by lichenification as a result of deliberate and repetitive scratching or rubbing.¹ LSC affects up to 12% of the population.² Peak incidence is between 30 and 50 years of age.³ The female to male ratio is approximately 2 to 1.⁴ It is more common in the Asian population.¹

ETIOPATHOGENESIS And Histopathology

The skin lesions of LSC are the end result of an itch-scratch cycle.³ Affected patients are more likely to respond to an itch stimulus than are control subjects; the underlying pathophysiology is not known.¹ Predisposing factors include mechanical irritation, xerosis, heat, sweating, anxiety, stress, depression, obsessive-compulsive disorder, and personal or family history of atopy.^1-3 LSC can occur de novo on normal skin and can also develop secondarily on preexisting dermatologic conditions such as atopic dermatitis, allergic contact dermatitis, and psoriasis.³

Histologic findings include epidermal hyperplasia with acanthosis, hyperkeratosis, hypergranulosis, dermal fibrosis with vertical streaking of collagen bundles, and a perivascular infiltrate of lymphocytes.^1,3,4

CLINICAL MANIFESTATIONS

Characteristically, the pruritus is intense, leading to a strong desire to scratch and initiating a vicious cycle. Typically, the pruritus is paroxysmal and worse at night.¹ It may be worsened with local heat, sweating, or scratching/rubbing.

Clinically, LSC presents as circumscribed, lichenified, pruritic patches. Early skin changes include erythema and slight edema.¹ With time, these changes subside, and the skin becomes thickened and leathery, with exaggeration of normal markings.¹ A circumscribed, lichenified plaque is the hallmark of LSC.¹ Both hypopigmentation and hyperpigmentation have been described, although the most common finding is a dusky violaceous or brown hyperpigmentation.¹ Scales and excoriations are often present. 

Sites of predilection include the neck, face, scalp, shoulders, and extensor surfaces, especially the wrists and ankles. The vulva, pubis, scrotum, back, and eyelids can also be affected.⁵ The mid-back is often spared given that it is hard to reach.

Affected patients have a greater tendency to pain avoidance, greater dependency on other peoples’ desires, and are more conforming and dutiful compared with the general population.⁶

DIAGNOSIS and Differential Diagnosis

The diagnosis of LSC is usually clinical, based on its distinctive clinical history and findings. A skin biopsy or referral to a dermatologist should be considered if the diagnosis is in doubt.

The differential diagnosis includes tinea corporis, nummular eczema, psoriasis, lichen planus, contact dermatitis, lichen amyloidosis, and mycosis fungoides (cutaneous T-cell lymphoma).¹

COMPLICATIONS, PROGNOSIS, And Management

LSC has a negative impact on quality of life and may lead to depression, anxiety, sleep disturbance, and sexual dysfunction.² It tends to run a chronic course, and recurrences are frequent. 

The patient should be advised that the condition will improve if scratching or rubbing of the affected area can be stopped. Fingernails should be cut very short. Covering the affected area may increase the healing rate by enhancing the effects of the topical medication and serving as a barrier to protect the skin from further trauma.² Any underlying stress should be removed if possible. This can be achieved through lifestyle modification. Moisturizers may help in repairing the skin.

Ultrapotent topical corticosteroids are the mainstay of therapy.¹ Topical immunomodulators (ie, tacrolimus and pimecrolimus) and low- to medium-potency corticosteroids are not as fast or effective in the treatment of LSC, although they can be considered in the maintenance phase. Lesions should be swabbed if there is any sign of infection. A corticosteroid-antibiotic combination can be particularly helpful for the eroded lesions, and occasionally oral antibiotics have to be used if infection is suspected. Oral sedating antihistamine can be used to relieve the itchiness. For persistent lichenified papules/plaques, intralesional corticosteroids should be considered.³ Rarely, for widespread and resistant lesions, a short course of oral corticosteroids or other immunosuppressants may be helpful; phototherapy can also be considered.³ Referral to a psychologist or psychiatrist may be necessary if there is significant psychological stress.

Alexander K. C. Leung, MD, is clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary, Alberta, Canada.

Benjamin Barankin, MD, is a dermatologist and the medical director and founder of the Toronto Dermatology Centre in Toronto, Ontario, Canada.

REFERENCES:

1. Prajapati V, Barankin B. Lichen simplex chronicus. Can Fam Physician. 2008;​54(10):1391-1393.

2. Liao Y-H, Lin C-C, Tsai P-P, Shen W-C, Sung F-C, Kao C-H. Increased risk of lichen simplex chronicus in people with anxiety disorder: a nationwide population-based retrospective cohort study. Br J Dermatol. 2014;170(4):890-894.

3. Lichen simplex chronicus (neurodermatitis; prurigo). Clinical Decision Support: Dermatology. http://www.decisionsupportinmedicine.com. Accessed October 14, 2016.

4. Lotti T, Buggiani G, Prignano F. Prurigo nodularis and lichen simplex chronicus. Dermatol Ther. 2008;21(1):42-46.

5. Rajalakshmi R, Thappa DM, Jaisankar TJ, Nath AK. Lichen simplex chronicus of anogenital region: a clinico-etiological study. Indian J Dermatol Venereol Leprol. 2011;77(1):28-36.

6. Martín-Brufau R, Corbalán-Berná J, Ramirez-Andreo A, Brufau-Redondo C, Limiñana-Gras R. Personality differences between patients with lichen simplex chronicus and normal population: a study of pruritus. Eur J Dermatol. 2010;20(3):359-363.